Index: channels/chan_agent.c
===================================================================
--- channels/chan_agent.c	(revision 143400)
+++ channels/chan_agent.c	(working copy)
@@ -2492,7 +2492,9 @@
 	/* First, take us out of the channel loop */
 	ast_channel_unregister(&agent_tech);
 	/* Delete devicestate subscription */
-	ast_event_unsubscribe(agent_devicestate_sub);
+	if (agent_devicestate_sub) {
+		ast_event_unsubscribe(agent_devicestate_sub);
+	}
 	/* Unregister dialplan functions */
 	ast_custom_function_unregister(&agent_function);	
 	/* Unregister CLI commands */